#include <arpa/inet.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#define MAX_EVENT_NUMBER 1024
#define BUFFER_SIZE 10

/* 将文件描述符设置成非阻塞 */
int setnonblocking(int fd) {
  int old_option = fcntl(fd, F_GETFL);
  int new_option = old_option | O_NONBLOCK;
  fcntl(fd, F_SETFL, new_option);
  return old_option;
}

/* 将文件描述符 fd 上的 EPOLLIN 注册到 epollfd 指示的 epoll 内核时间表种， 参数
 * enbale_et 指定是否对 fd 启用 ET 模式 */
void add_fd(int epollfd, int fd, int enable_et) {
  struct epoll_event event;
  event.data.fd = fd;
  event.events = EPOLLIN;
  if (enable_et) {
    event.events |= EPOLLET;
  }
  epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
  setnonblocking(fd);
}

/* LT 模式工作流程 */
void lt(struct epoll_event *events, int number, int epollfd, int listenfd) {
  char buf[BUFFER_SIZE];
  for (int i = 0; i < number; ++i) {
    int sockfd = events[i].data.fd;
    if (sockfd == listenfd) {
      struct sockaddr_in client_address;
      socklen_t client_addrlength = sizeof(client_address);
      int connfd = accept(listenfd, (struct sockaddr *)&client_address,
                          &client_addrlength);
      /* 对 connfd 禁用 et 模式 */
      add_fd(epollfd, connfd, 0);
    } else if (events[i].events & EPOLLIN) {
      /* 只要 socket 读缓存中还有未读出的数据，这段代码就被触发 */
      printf("event trigger once\n");
      memset(buf, 0x0, BUFFER_SIZE);
      int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
      if (ret <= 0) {
        close(sockfd);
        continue;
      }
      printf("get %d bytes of content: %s\n", ret, buf);
    } else {
      printf("something else happened.\n");
    }
  }
}

/* ET 模式工作流程 */
void et(struct epoll_event *events, int number, int epollfd, int listenfd) {
  char buf[BUFFER_SIZE];
  for (int i = 0; i < number; ++i) {
    int sockfd = events[i].data.fd;
    if (sockfd == listenfd) {
      struct sockaddr_in client_address;
      socklen_t client_addrlength = sizeof(client_address);
      int connfd = accept(listenfd, (struct sockaddr *)&client_address,
                          &client_addrlength);
      add_fd(epollfd, connfd, 1);
    } else if (events[i].events & EPOLLIN) {
      /* 这段代码不会被重复触发，需要循环读取数据，确保把 socket
       * 缓存区中的数据全部读出 */
      printf("event trigger once\n");
      while (1) {
        memset(buf, 0x0, BUFFER_SIZE);
        int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
        if (ret < 0) {
          /* 对于非阻塞 IO，下面的条件成立表示数据已经全部读取完毕。此后，epoll
           * 就能被再次触发 sockfd 上的 EPOLLIN 事件，以驱动下一次读事件 */
          if (errno == EAGAIN || errno == EWOULDBLOCK) {
            printf("read later\n");
            break;
          }
          close(sockfd);
          break;
        } else if (ret == 0) {
          close(sockfd);
        } else {
          printf("get %d bytes of content: %s\n", ret, buf);
        }
      }
    } else {
      printf("something else happened\n");
    }
  }
}

int main(int argc, char *argv[]) {
  const char *ip = argv[1];
  int port = atoi(argv[2]);

  int ret = 0;
  struct sockaddr_in address;
  bzero(&address, sizeof(address));
  address.sin_family = AF_INET;
  inet_pton(AF_INET, ip, &address.sin_addr);
  address.sin_port = htons(port);

  int listenfd = socket(PF_INET, SOCK_STREAM, 0);
  assert(listenfd >= 0);
  ret = bind(listenfd, (struct sockaddr *)&address, sizeof(address));
  assert(ret != -1);
  printf("绑定成功\n");
  ret = listen(listenfd, 5);
  assert(ret != -1);

  struct epoll_event events[MAX_EVENT_NUMBER];
  int epollfd = epoll_create(5);
  assert(epollfd != -1);
  add_fd(epollfd, listenfd, 1);

  while (1) {
    int ret = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
    if (ret < 0) {
      printf("epoll failure");
      break;
    }
    // lt(events, ret, epollfd, listenfd);
    et(events, ret, epollfd, listenfd);
  }
  close(listenfd);
  return 0;
}